Thyroid Incidentalomas Research Articles

Thyroid Lobectomy for Low-Risk 1–4 CM Papillary Thyroid Cancer is not Associated with Increased Recurrence Rates in the Dutch Population with a Restricted Diagnostic Work-Up

IntroductionThe 2015 American Thyroid Association guidelines recommend to de-escalate treatment such as Thyroid lobectomy instead of total thyroidectomy for 1–4 cm papillary thyroid cancer (PTC). Dutch guidelines endorse restricted work-up for thyroid incidentalomas recommending only fine needle aspiration in case of a ‘palpable thyroid nodule’. This diagnostic work-up algorithm may result in the identification of less indolent PTCs and may lead to a patient population with relatively more aggressive PTCs. This study aims to retrospectively analyze recurrence rates of low-risk 1–4 cm PTC in the Netherlands.MethodsFrom the national cancer registry, patients with low-risk 1–4 cm PTC between 2005 and 2015 were included for analysis. Disease free survival (DFS) and overall survival were compared between patients who underwent TT ± RAI and TL without RAI. Post-hoc propensity score analysis was performed correcting for age, sex, T-stage, and N-stage.ResultsIn total 901 patients were included, of which 711 (78.9%) were females, with a median follow-up of 7.7 years. TT was performed in 893 (94.8%) patients. Recurrence occurred in 23 (2.6%) patients. Multivariable analysis showed no significant correlation between extent of surgery and DFS (p = 0.978), or overall survival (p = 0.590). After propensity score matching, multivariable analysis showed no significant difference on extent of surgery and recurrence.ConclusionLow-risk PTC patients with 1–4 cm tumor who underwent TL showed similar recurrence rates as those who underwent TT ± adjuvant RAI, which suggests that TL can be sufficient in treating low-risk 1–4 cm PTC, possibly reducing morbidity of these patients in the Netherlands.

569. INCIDENCE AND ONCOLOGICAL IMPLICATIONS OF THYROID INCIDENTALOMAS IN ESOPHAGEAL CANCER PATIENTS

Abstract Although thyroid incidentalomas are regularly encountered during imaging of esophageal cancer, their oncological significance remains unknown. The aim of this study was to describe the incidence and etiology of thyroid incidentalomas observed during the diagnostic workup of esophageal cancer patients. This retrospective cohort study included all esophageal cancer patients referred to or diagnosed in the Amsterdam UMC between January 2012 and December 2016. Radiology and multidisciplinary team meeting reports were reviewed for thyroid incidentalomas. In case of thyroid incidentaloma, the 18FDG-PET/CT or CT was reassessed by a radiologist blinded for the original report. The primary outcome was the incidence and etiology of thyroid incidentalomas. This study included 1,110 esophageal cancer patients, with a median age of 66 years. Most patients were male (77.2%) and had an adenocarcinoma (69.4%). Thyroid incidentalomas were reported in 115 patients (10.4%)/ In 23 (20.0%) patients, additional diagnostics were required to characterize the lesion and two thyroidal lesions proved malignant. One patient was diagnosed with an esophageal cancer metastasis and one patient with a primary thyroid carcinoma. Only the primary thyroid carcinoma resulted in treatment alteration. The other malignant thyroid incidentaloma was in the context of generalized disseminated esophageal disease and no longer eligible for curative treatment. In this study, thyroid incidentalomas were regularly observed, although their oncological significance is limited. Therefore, further etiological examination of thyroidal incidentaloma should only be considered when clinical consequences are to be expected.

The value of 99mTc-MIBI scan in the detection of malignancy potential of hypermetabolic thyroid incidentalomas of 18F-FDG PET/CT

Aim of the studyIncreasingly use of PET/CT leads to discovery of incidental findings. Hypermetabolic thyroid nodules are one of the unexpected lesions in PET/CT imaging with an increased risk of thyroid cancers. Our study aims to determine the malignant potential of incidentally detected 18F-FDG avid thyroid nodules by using Tc-99m MIBI imaging. Materials and methodsPET/CT scans were performed for nonthyroidal purposes and were evaluated for the presence of hypermetabolic thyroid nodules. Tc-99m MIBI scans and ultrasonography-guided fine needle aspiration biopsies were subsequently performed for all patients. ResultsPrimary thyroid malignancies were identified in 25% of patients with increased focal FDG uptake at definitive diagnosis. Among the patients with FDG avid thyroid nodules, Tc-99m MIBI scan showed true-positive results in all thyroid carcinomas (n:7) with a 36.3% (4/11) false-positivity rate. In three patients with indeterminate cytology results, Tc-99m MIBI scan findings were also negative. The sensitivity, specificity, positive predictive value of Tc-99m MIBI scan in predicting the malignancy of FDG-positive thyroid nodules were 100%, 77%, 63.6%, respectively. ConclusionThe implementation of 99mTc-MIBI scan performed by dual phase and SPECT/CT modality might be a helpful cost-effective approach in addition to FNAB in patients with 18F-FDG-positive thyroid nodules and indeterminate cytology to improve the patients’ prognosis and reduce unnecessary thyroid operations with associated use of FNAB.

Thyroid incidentalomas: which features in internal medicine?

Thyroid incidentalomas: which features in internal medicine?

Influence of Incidental Detection of Thyroid Nodule on Thyroid Cancer Risk and Prognosis – A Systematic Review and Meta-analysis

Abstract Background Clinically inapparent thyroid nodules discovered serendipitously on imaging for non-thyroid indications are termed as thyroid incidentalomas. It is unclear whether these incidentalomas have a lower prevalence of malignancy or slower tumour progression compared to symptomatic nodules. The aim of this systematic review were to determine the impact of incidental detection of thyroid nodules on both the risk of malignancy and on prognosis in patients with thyroid cancer. Methods PubMed and MEDLINE® on Web of Science databases were searched from inception to April 2021 for English language articles reporting on human studies of thyroid cancer risk and/or prognosis in incidental and non-incidental nodules. Results Eighteen observational studies published between 1998 and 2020 were eligible for analysis; 4 studies reported on risk, 9 on prognosis and 5 studies reported on both risk and prognosis. When comparing the incidental and non-incidental groups in the risk study, the odds ratios calculated from the case control studies (n=6) ranged from 0.64 to 2.86; the relative risks calculated from the cohort studies (n=3) ranged from 0.13 to 6.27. A meta-analysis of the eligible case control studies (n=3) showed a non-significant summated odds ratio of 1.04 (95% CI=0.63–1.70, p=0.88). In the prognosis study, five direct and thirteen indirect markers of prognosis were compared between the incidental and non-incidental groups. A meta-analysis was not possible but incidentally detected thyroid cancer had better progression-free and overall survival. Conclusion Current evidence suggests that investigation and management of thyroid nodules should not be influenced by the mode of detection. However, incidentally detected nodules appear to have a better prognosis.

Radiomics Analysis of [18F]FDG PET/CT Thyroid Incidentalomas: How Can It Improve Patients' Clinical Management? A Systematic Review from the Literature.

Background: We performed a systematic review of the literature to provide an overview of the application of PET-based radiomics of [18F]FDG-avid thyroid incidentalomas and to discuss the additional value of PET volumetric parameters and radiomic features over clinical data. Methods: The most relevant databases were explored using an algorithm constructed based on a combination of terms related to our subject and English-language articles published until October 2021 were considered. Among the 247 identified articles, 19 studies were screened for eligibility and 11 met the criteria, with 4 studies including radiomics analyses. Results: We summarized the available literature based on a study of PET volumetric parameters and radiomics. Ten articles provided accurate details about volumetric parameters and their prospective value in tumour assessment. We included the data provided by these articles in a sub-analysis, but could not obtain statistically relevant results. Four publications analyzed the diagnostic potential of radiomics and the possibility of creating precise predictive models, their corresponding quality score being assessed. Conclusions: The use of PET volumetric parameters and radiomics analysis in patients with [18F]FDG-avid thyroid incidentalomas outlines a great prospect in diagnosis and stratification of patients with malignant nodules and may represent a way of limiting the need for unnecessary invasive procedures; however, further studies need to be performed for a standardization of the method.

'The clinical decision making for 18FDG-PET/CT thyroid incidentaloma in cancer patients'

Background: 18Fluorodeoxyglucose (|FDG)--avid thyroid incidentaloma (TI) is seen in approximately 2.5% of cancer patients who undergo 18FDG-Positron Emission Tomography / Computed Tomography (PET/CT) for staging or treatment response assessment and represents thyroid cancer in approximately 30% of cases. The 2015 American Thyroid Association (ATA) guidelines recommend investigation of thyroid nodules 1 cm or larger with ultrasound and possible fine-needle aspiration cytology (FNAC). This study aimed to determine the prognostic value of additional diagnostics for TI in cancer patients and to analyze their survival.

Comparison between Two Different Scanners for the Evaluation of the Role of 18F-FDG PET/CT Semiquantitative Parameters and Radiomics Features in the Prediction of Final Diagnosis of Thyroid Incidentalomas.

The aim of this study was to compare two different tomographs for the evaluation of the role of semiquantitative PET/CT parameters and radiomics features (RF) in the prediction of thyroid incidentalomas (TIs) at 18F-FDG imaging. A total of 221 patients with the presence of TIs were retrospectively included. After volumetric segmentation of each TI, semiquantitative parameters and RF were extracted. All of the features were tested for significant differences between the two PET scanners. The performances of all of the features in predicting the nature of TIs were analyzed by testing three classes of final logistic regression predictive models, one for each tomograph and one with both scanners together. Some RF resulted significantly different between the two scanners. PET/CT semiquantitative parameters were not able to predict the final diagnosis of TIs while GLCM-related RF (in particular GLCM entropy_log2 e GLCM entropy_log10) together with some GLRLM-related and GLZLM-related features presented the best predictive performances. In particular, GLCM entropy_log2, GLCM entropy_log10, GLZLM SZHGE, GLRLM HGRE and GLRLM HGZE resulted the RF with best performances. Our study enabled the selection of some RF able to predict the final nature of TIs discovered at 18F-FDG PET/CT imaging. Classic semiquantitative and volumetric PET/CT parameters did not reveal these abilities. Furthermore, a good overlap in the extraction of RF between the two scanners was underlined.

Impact of Thyroid Incidentaloma on Liver Transplant: A Study of 1010 Recipients at a Single Center.

BackgroundThyroid incidentalomas are typically nonpalpable thyroid nodules discovered during radiographic evaluation for a non-thyroid issue. Thyroid incidentalomas visualized by computed tomography (CT) and 18F-flurodeoxyglucose (FDG) positron emission tomography (PET) before living donor liver transplantation (LDLT) are rare. The aim of the study was to analyze the clinical impact of thyroid incidentalomas discovered prior to transplantation.Material/MethodsThis retrospective study recruited 1010 patients undergoing LDLT between 2010 and 2019. CT was performed on each patient, whereas PET was performed on randomized patients (n=498).ResultsThe prevalence and malignant risk of thyroid incidentaloma on CT was 2.3% (23/1010) and 13.0% (3/23), respectively. The prevalence of thyroid incidentaloma on PET was 3.0% (15/498). Approximately half of the FDG uptake on PET was diffuse uptake (n=7), whereas the other half was focal uptake (n=8). The malignant risk of PET incidentaloma with focal FDG uptake was 37.5% (3/8). Four asymptomatic thyroid cancers were identified incidentally. After total thyroidectomy followed by LDLT, these patients maintained cancer-free status.ConclusionsThyroid incidentalomas occurred at a rate of 2–3% in LDLT candidates. The malignant risk was 13.0% on CT incidentaloma, and 37.5% on PET incidentaloma with focal FDG uptake. Curative treatment of incidental thyroid cancer followed by LDLT without delay can achieve a favorable prognosis.

Retrospective analysis of PSMA PET/CT thyroid incidental uptake in adults: incidence, diagnosis, and treatment/outcome in a tertiary cancer referral center and University Medical Center.

A prostate-specific membrane antigen (PSMA) thyroid incidentaloma (PTI) is an unexpected, PSMA-avid thyroid lesion, newly detected during the investigation of an unrelated condition using PSMA PET/CT. The aim of this study is to examine the incidence and clinical significance of PTI and the associated management strategies since the implementation of the PSMA PET/CT scan. This study involves a retrospective cohort study of 61 PTI cases depicted on PSMA PET/CT scans performed between January 2016 and July 2021, almost exclusively for (re)staging prostate cancer. The medical records of the included cases were retrospectively reviewed and data of the PSMA PET/CT scans, primary malignancy, thyroid diagnostics, treatment, and follow-up were collected. PTI was reported in 1.1% of the patients who underwent oncologic PSMA PET/CT scans included in this study. Two PTI cases had a histologically proven thyroid cancer: one a benign thyroid lesion and one a metastasis of a renal cell carcinoma. In none of the cases in whom any form of further thyroid workup was withheld, the PTI became clinically relevant during follow-up (median 1.8years (1.1-3.3)). Six patients (10%) died due to their primary cancer. The incidence of thyroid incidentalomas on PSMA PET/CT was low (1.1%) in this large, two-center experience. Less than half of the PTI cases were analyzed and the risk of malignancy, despite being low, was not negligible. The clinical outcome was good using a standard diagnostic workup for PTI, while the prognosis of the patient was determined by the primary malignancy. The consideration to analyze and treat PTI cases should be part of the shared decision-making in cancer patients.

Characterization of focal hypermetabolic thyroid incidentaloma: An analysis with F-18 fluorodeoxyglucose positron emission tomography/computed tomography parameters.

BACKGROUNDIncidentally found thyroid tumor (thyroid incidentaloma, TI) on F-18 fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) is reported in 2.5%-5% of patients being investigated for non-thyroid purposes. Up to 50% of these cases have been diagnosed to be malignant by cytological/histological results. Ultrasonography (US) and fine-needle aspiration cytology are recommended for thyroid nodules with high FDG uptake (hypermetabolism) that are 1 cm or greater in size. It is important to accurately determine whether a suspicious hypermetabolic TI is malignant or benign.AIMTo distinguish malignant hypermetabolic TIs from benign disease by analyzing F-18 FDG PET-CT parameters and to identify a cut-off value.METHODSTotally, 12761 images of patients who underwent F-18 FDG PET-CT for non-thyroid purposes at our hospital between January 2016 and December 2020 were retrospectively reviewed, and 339 patients [185 men (mean age: 68 ± 11.2) and 154 women (mean age: 63 ± 15.0)] were found to have abnormal, either focal or diffuse, thyroid FDG uptake. After a thorough review of their medical records, US, and cytological/histological reports, 46 eligible patients with focal hypermetabolic TI were included in this study. The TIs were categorized as malignant and benign according to the cytological/histological reports, and four PET parameters [standardized uptake value (SUV)max, SUVpeak, SUVmean, and metabolic tumor volume (MTV)] were measured on FDG PET-CT. Total lesion glycolysis (TLG) was calculated by multiplying the SUVmean by MTV. Both parametric and non-parametric methods were used to compare the five parameters between malignant and benign lesions. Receiver operating characteristic (ROC) curve analysis was performed to identify a cut-off value.RESULTSEach of the 46 patients [12 men (26.1%; mean age: 62 ± 13.1 years) and 34 women (73.9%; mean age: 60 ± 12.0 years)] with focal hypermetabolic TIs had one focal hypermetabolic TI. Among them, 26 (56.5%) were malignant and 20 (43.5%) were benign. SUVmax, SUVpeak, SUVmean, and TLG were all higher in malignant lesions than benign ones, but the difference was statistically significant (P = 0.012) only for SUVmax. There was a positive linear correlation (r = 0.339) between SUVmax and the diagnosis of malignancy. ROC curve analysis for SUVmax revealed an area under the curve of 0.702 (P < 0.05, 95% confidence interval: 0.550-0.855) and SUVmax cut-off of 8.5 with a sensitivity of 0.615 and a specificity of 0.789.CONCLUSIONMore than half of focal hypermetabolic TIs on F-18 FDG PET-CT were revealed as malignant lesions, and SUVmax was the best parameter for discriminating between malignant and benign disease. Unexpected focal hypermetabolic TIs with the SUVmax above the cut-off value of 8.5 may have a greater than 70% chance of malignancy; therefore, further active assessment is required.

Focal Thyroid Incidentalomas on 18F-FDG PET/CT: A Systematic Review and Meta-Analysis on Prevalence, Risk of Malignancy and Inconclusive Fine Needle Aspiration.

BackgroundThe rising demand for 18F-fluorodeoxyglucose positron emission tomography with computed tomography (18F-FDG PET/CT) has led to an increase of thyroid incidentalomas. Current guidelines are restricted in giving options to tailor diagnostics and to suit the individual patient.ObjectivesWe aimed at exploring the extent of potential overdiagnostics by performing a systematic review and meta-analysis of the literature on the prevalence, the risk of malignancy (ROM) and the risk of inconclusive FNAC (ROIF) of focal thyroid incidentalomas (FTI) on 18F-FDG PET/CT.Data SourcesA literature search in MEDLINE, Embase and Web of Science was performed to identify relevant studies.Study SelectionStudies providing information on the prevalence and/or ROM of FTI on 18F-FDG PET/CT in patients with no prior history of thyroid disease were selected by two authors independently. Sixty-one studies met the inclusion criteria.Data AnalysisA random effects meta-analysis on prevalence, ROM and ROIF with 95% confidence intervals (CIs) was performed. Heterogeneity and publication bias were tested. Risk of bias was assessed using the quality assessment of diagnostic accuracy studies (QUADAS-2) tool.Data SynthesisFifty studies were suitable for prevalence analysis. In total, 12,943 FTI were identified in 640,616 patients. The pooled prevalence was 2.22% (95% CI = 1.90% - 2.54%, I2 = 99%). 5151 FTI had cyto- or histopathology results available. The pooled ROM was 30.8% (95% CI = 28.1% - 33.4%, I2 = 57%). 1308 (83%) of malignant nodules were papillary thyroid carcinoma (PTC). The pooled ROIF was 20.8% (95% CI = 13.7% - 27.9%, I2 = 92%).LimitationsThe main limitations were the low to moderate methodological quality of the studies and the moderate to high heterogeneity of the results.ConclusionFTI are a common finding on 18F-FDG PET/CTs. Nodules are malignant in approximately one third of the cases, with the majority being PTC. Cytology results are non-diagnostic or indeterminate in one fifth of FNACs. These findings reveal the potential risk of overdiagnostics of FTI and emphasize that the workup of FTI should be performed within the context of the patient’s disease and that guidelines should adopt this patient tailored approach.

Retrospective Analyses of 18FDG-PET/CT Thyroid Incidentaloma in Adults: Incidence, Treatment, and Outcome in a Tertiary Cancer Referral Center.

Background: A thyroid incidentaloma (TI) is an unexpected, asymptomatic thyroid lesion discovered during the investigation of an unrelated condition. The aim of the present study is to examine the incidence of 18Fluorodeoxyglucose (FDG)-positron emission tomography (PET) TI, the associated management strategies and the outcomes in a tertiary cancer referral center. Methods: This study involves a retrospective cohort study of 1003 patients with TI found on 18FDG-PET/CT scans performed between January 2010 and January 2020 for a nonthyroidal malignancy. The Kaplan-Meier method was used for survival analyses in patients concerning an underlying malignancy, with a prevalence of 5% or higher in this cohort. Logistic- and cox regression analyses were performed to analyze predictors of thyroid malignancy and mortality. A propensity score weighted method was used to control for baseline differences between the intervention (additional TI diagnostics) and control (no TI diagnostics) group. Results: FDG-positive TI occurred in 1.9% (1003/52,693) of the oncologic 18FDG-PET/CT scans performed in our center. Thyroid surgery was performed in 47 patients (6%) and a thyroid malignancy was detected in 31 of them, which is 66% of those who had an operation and 4% of all patients. During the follow-up (median 6 years), 334 deaths (42%) related to different types of cancer (38%) or other causes (4%) were observed. One patient died from medullary thyroid cancer. In multivariate analysis adjusted for age, gender and the type- and stage of nonthyroidal malignancy, were independent predictors of survival (P < .05). Conclusions: The incidence of TI in this tertiary cancer referral center was comparable to current literature. Further thyroid workup was performed in less than half of the patients, and only a minority of patients underwent thyroid surgery. Since only one patient died from thyroid cancer, the strategy to withhold from thyroid diagnostics and treatment seems valid for most TI. Active thyroid treatment might benefit a subgroup of patients in whom the primary nonthyroidal malignancy is successfully treated or presumably stable. A wait-and-see policy with ultrasound follow-up could be an alternative strategy. These considerations should be part of the shared decision making in cancer patients with a TI.

Hospital-Based Ultra-Sonographic Prevalence and Spectrum of Thyroid Incidentalomas in Pakistani Population.

Introduction: Thyroid incidentalomas (TIs) are clinically asymptomatic nodules found accidentally during imaging studies ordered for some other reasons. Being easily accessible, non-invasive, and inexpensive, thyroid ultrasound (US) is a key investigation in the management of thyroid nodules.Methods: This ultrasound-based cross-sectional study was performed in the radiology department of a major tertiary care hospital. Every second patient visiting the emergency department was a potential candidate for a thyroid ultrasound. Patients having ages greater than 20 years were included in the study.Results: A total of 250 patients were included in the study. Out of these, 175 were female and 75 were male. The majority (54.80%) were in the age group 21-30 years. Nodules were found in 65 (26%) patients and in the majority of cases (67.7%) they were multiple in number. Associated lymphadenopathy was seen in only one patient. Thyroid nodules were more common in females as compared to males (75.38% versus 24.62%). According to Thyroid Imaging and Reporting Data System (TI-RADS) classification, the majority of the nodules were falling in TI-RADS 1 (74%) followed by TI-RADS 3 (9.60%) and 4A (8.80%).Conclusion: The thyroid nodules are more commonly seen in females as compared to males. A significant association is seen between the frequency of thyroid nodules and increasing age. The majority of thyroid nodules fall in TI-RADS 1 category followed by TI-RADS 3 and 4A.

The influence of incidental detection of thyroid nodule on thyroid cancer risk and prognosis-A systematic review.

Clinically inapparent thyroid nodules discovered serendipitously on imaging for nonthyroid indications are termed as thyroid incidentalomas. It is unclear whether these incidentalomas have a lower prevalence of malignancy or slower tumour progression compared to symptomatic nodules. The aims of this systematic review were to determine the impact of incidental detection of thyroid nodules on both the risk of malignancy and on prognosis in patients with thyroid cancer. PubMed and MEDLINE® on Web of Science databases were searched from inception to March 2020 for English language articles reporting on human studies of thyroid cancer risk and/or prognosis in incidental and nonincidental nodules. Eighteen observational studies published between 1998 and 2020 were eligible for analysis; four studies reported on risk, nine on prognosis and five studies reported on both risk and prognosis. When comparing the incidental and nonincidental groups in the risk study, the odds of incidental detection in the cancer and benign groups ranged from 0.16 to 0.5 and 0.06 to 0.38, respectively (odds ratio [OR] = 0.64-2.86) in case-control studies (n = 6); the risk of malignancy for thyroid nodules ranged from 4% to 23.5% in the incidental and 3.8% to 28.7% in the nonincidental groups (relative risk = 0.13-6.27) in the cohort studies (n = 3). A meta-analysis of the eligible case-control studies (n = 3) showed a nonsignificant summated OR of 1.04 (95% confidence interval = 0.63-1.70; p = .88). In the prognosis study, five direct and thirteen indirect markers of prognosis were compared between the incidental and nonincidental groups. A meta-analysis was not possible but incidentally detected thyroid cancer had better progression-free and overall survival. Current evidence suggests that investigation and management of thyroid nodules should not be influenced by the mode of detection.

Thyroid incidentaloma: next to be neglected or investigated?

In modern clinical practice, thyroid incidentaloma is an unpalpated node in the thyroid gland, which is detected accidentally by technical means of imaging when examining a patient for other, non-thyroid diseases. Its dimensions are limited to 10mm, the limit above which it can already be palpated by a qualified professional. In the author’s view, such a definition narrows the concept of incidentaloma, primarily from a nosological point of view. Under the definition of the node can be micro- or macrofollicular nodular goiter, tumor, benign (adenoma) or malignant (carcinoma), the focus of thyroiditis, cyst, inflammatory focus (infiltrate, abscess), calcifications. When enumerating the methods of detection by incidental, the palpation method is excluded and the nodes in the thyroid gland detected with its help are not only up to 10 mm in size but also larger, which should also be called incidental. The same can be said about the nodes that are accidentally found on the neck during operations for diseases of the trachea, cervical esophagus, salivary glands. Speaking of incidentalomas, which are detected at autopsy, it should be noted that some of them are larger than 10 mm. All these positions do not fit into the definition of thyroid incidentaloma only as an unpalpated node in the thyroid gland up to 10 mm, which is determined by instrumental imaging methods. Therefore, the concept of thyroid incidentaloma is broader and more capacious than formulated by its modern definition. Incidental thyroid disease should be considered any additional formation in it, regardless of its size, detected by any non-target method of research. Unpalpated and, as a rule, clinically “dumb” nodes up to 10 mm, determined by instrumental methods, can be considered as one of the subspecies of the incidentaloma. The frequency of their detection has increased sharply in recent years, some are malignant neoplasms with an unpredictable course, tactical approaches to them have not been finalized.

Malignancy Risk in 18F-FDG-Avid Thyroid Incidentalomas: Controversies and Limitations

Introduction: The prevalence of malignancy in thyroid incidentalomas (TI) discovered on 18F-FDG-PET or PET/CT varies between 0% and 63.6%. The pooled malignancy rate according to three systematic reviews is 33-35%. The 2015 American Thyroid Association (ATA) guidelines recommend that such nodules, when one centimeter or larger in size, should undergo further investigation with thyroid ultrasound (US) and fine-needle aspiration (FNA) cytology. Objectives: The objective of our study was to determine the rate of malignancy amongst TI discovered incidentally on 18F-FDG-PET or PET/CT, examine their clinicopathologic characteristics, and assess the usefulness of maximum standardized uptake values (SUVmax) in differentiating benign and malignant lesions. Methods: We performed an electronic medical record search looking at all 18F-FDG-PET or PET/CT reports during the study period of 12/01/2015 to 05/31/2019 that included the keyword ‘thyroid’ in the impression. Exclusion criteria included a history of thyroid disease or malignancy, known lesion(s) detected on previous clinical or radiological examinations and diffuse radiotracer uptake. Of the 476 reports reviewed, 136 cases were included in the study. Results: Common indications included initial staging or restaging of lymphoma (diffuse large B-cell, mantle-cell, T-cell types) (27.9%), lung adenocarcinoma (18.4%), head and neck cancer (16.9%) and breast cancer (11%). Fifty-eight (42.6%) patients had metabolically inactive lesions; five (8.6%) underwent further investigation with thyroid US and 3 subsequently with FNA (5%). All 3 had benign cytology. Seventy-seven (56.6%) patients had metabolically active lesions and 25 (32.5%) underwent imaging with thyroid US. Twelve (15.6%) had FNA; eight (66.7%) had benign cytology, two (16.7%) revealed atypia of undetermined significance and two (16.7%) were malignant. Biopsy for the two patients with malignant cytology showed follicular cell neoplasm of oncocytic hurtle cell type, and invasive follicular carcinoma with focal insular and papillary features and extensive capsular and vascular invasion. The mean SUVmax in malignant vs benign lesions was 9.05 and 6.41 respectively. Conclusion: The malignancy rate was 2.6% amongst all patients with 18F-FDG-avid TI and 8% amongst patients with metabolically active lesions who were investigated with thyroid US+/- FNA. This is significantly lower than malignancy rates previously reported in the literature. The evident inhomogeneity in the literature is likely multifactorial and may be explained in part by a dissimilarity among studies, and an informed decision by some to avoid invasive testing in the context of poor prognosis from underlying non-thyroidal cancer. Research is needed to determine the cohort of patients who could potentially benefit from further evaluation and treatment.

The Influence of Incidental Detection of Thyroid Nodule on Thyroid Cancer Risk and Prognosis - a Systematic Review

Clinically unapparent thyroid nodules discovered serendipitously on imaging for non-thyroid indications are termed ‘thyroid incidentalomas’. The increase in the detection of these incidentalomas (which are known to be very common) has been attributed to the widespread use of diagnostic imaging and the increase in sensitivity and resolution of these modalities. It is unclear whether these incidentalomas have a lower prevalence of thyroid cancer or slower tumour progression compared to symptomatic thyroid nodules. This systematic review aimed to determine the risk of malignancy in incidentally detected thyroid nodules and its impact on prognosis in patients with thyroid cancer. PubMed and MEDLINE® on Web of Science databases were searched from inception to March 2020 for English language articles reporting on human studies of thyroid cancer risk and/or prognosis in incidental and non-incidental nodules. Quality of included studies was assessed using the Newcastle-Ottawa Scale (NOS). Seventeen observational studies published between 1998 and 2018 were eligible for analysis; 4 studies reported on risk, 8 studies on prognosis and 5 studies on both risk and prognosis. In the risk review, the odds ratios calculated from the six case-control studies (3246 patients) ranged from 0.64 to 2.86 whilst the relative risks calculated from the three cohort studies (489 patients) ranged from 0.13 to 6.27. NOS score for included risk studies (n=9) ranged from 22.2% to 66.7%. A meta-analysis of the eligible case-control studies (n=3) showed a non-significant summated odds ratio of 1.04 (95% CI=0.63-1.70, p=0.88). In the prognosis review of thirteen studies, three direct and thirteen indirect markers of prognosis were compared between the incidental (1923 patients) and non-incidental (2639 patients) groups. NOS score for included prognosis studies ranged from 66.7% to 100%. Incidentally detected thyroid nodules were significantly more likely to be smaller, have lower rates of extra-thyroidal and extra-nodal extension and lymph node metastasis, and interestingly more likely to have advanced disease. Other indirect prognostic markers were not shown to be significantly different between the two groups. A meta-analysis was not possible but incidentally detected thyroid cancer had better progression-free and overall survival; this finding may be affected by ‘lead time’ bias. Current evidence suggests that the investigation and management of thyroid nodules should not be influenced by the mode of detection.

Thyroid incidentalomas with increased focal 18F-FDG uptake in 18F-FDG PET/CT of a patient with multiple primary cancers.

Thyroid incidentalomas with increased focal 18F-FDG uptake in 18F-FDG PET/CT of a patient with multiple primary cancers.

The dilemma of 18F-FDG PET/CT thyroid incidentaloma: what we should expect from FNA. A systematic review and meta-analysis

Purpose18F-FDG thyroid incidentaloma (TI) occurs in ~2% of PET/CT examinations with a cancer prevalence of up to 35–40%. Guidelines recommend fine-needle aspiration cytology (FNA) if a focal 18F-FDG TI corresponds to a sonographic nodule >1 cm. The aim of this systematic review and meta-analysis was to provide evidence-based data on the diagnostic distribution of 18F-FDG TIs in the six Bethesda systems for reporting thyroid cytopathology (BETHESDA) subcategories.MethodsOriginal studies reporting 18F-FDG TIs and cytologically classified according to BETHESDA were included. Six separate meta-analyses were performed to obtain the pooled prevalence (95% confidence interval, 95% CI) of 18F-FDG TIs in the six BETHESDA subcategories.ResultsFifteen studies were finally included. Nine studies were from Asian/Eastern and six from Western countries. FNA data according to BETHESDA was available in 2304 cases. The pooled prevalence of 18F-FDG TIs according to BETHESDA was BETHESDA I 10% (6–14), BETHESDA II 45% (37–53), BETHESDA III 8% (3–13), BETHESDA IV 8% (5–12), BETHESDA V 6% (4–9), BETHESDA VI 19% (13–25). A significantly different prevalence was found in the BETHESDA IV between Asian/Eastern (2%) and Western (19%) studies.ConclusionTwo-thirds of focal 18F-FDG TIs undergoing FNA have either malignant (BETHESDA VI) or benign (BETHESDA II) cytology while a minority will have indeterminate (BETHESDA III or IV) FNA results. Significant differences between Asian/Eastern and Western studies are also present in the prevalence of indeterminate FNA results.